The overall goal of the proposed study is to develop a culturally and linguistically appropriate measure of children's word-learning ability that can be used for a range of assessment purposes. The proposed project will refine a previously developed expressive word learning tool using dynamic assessment of quick incidental learning and evaluate the tool's diagnostic accuracy. The project will also evaluate the linguistic and environmental factors that influence performance on vocabulary and word-learning measures. Accurate assessment of vocabulary skills is vital but also complex. Clinicians often use standard static vocabulary assessments as a measure of lexical acquisition despite the growing body of evidence that has shown that scores on standard static vocabulary assessments correlate with variables other than semantic knowledge including maternal education and socioeconomic status. Because static assessment tools measure experience dependent knowledge, children from nonmainstream backgrounds, whose experience may differ from test expectations, are at particular risk for begin misidentified as having language disabilities even if they have intact language-learning mechanisms. Thus, a gap exists in our ability to appropriately assess word-learning abilities in all populations. To address this gap, this study will evaluate whether a dynamic assessment of word-learning ability is a better reflection of vocabulary potential than traditional static measures for children from high-risk backgrounds.